Inductor devices



atent fi ice 2,958,060 Patented Oct. 25, 1 960 'INDUCTOR'DEVICES Martin0. Kalb, Bronx, N.Y., assignor to American Machine 8: Foundry Company, acorporation of New Jersey Filed Aug. 6, 1956, Ser. No. 602,205

2 Claims. (Cl. 336-210) This invention'relates to electromagneticinductor devices and, more particularly, to inductor devices utilizingcores wound from a continuous strip of magnetic material.

Magnetic cores formed of relatively thin, continuous strip magneticmaterial and wound to form laminated core elements are generallyemployed for inductors when his desirable to obtain bettermagnetic-properties than can be obtained when conventional stampedlaminations are used. One reason for such improved magnetic propertiesis the fact that the grain of the iron material comprising the strip'isso oriented asto be coincidental with the lines of magnetic flux set uptherein.

In practice, the coil windings associated with acontinuous type core arewound as separate units to a desired configuration and then mounted on.the continuously wound core. Inasmuch as both the core and the coilwindings are generally constructed as continuous ring elements, toarrange them in an interlocked relationship requires that the coreitself be parted to permit insertion of the coil on one or more legsthereof. The core must then be closed again to establish a minimumresidual gap or a selected gap thickness, particularly for applicationswhere D.C.-exists in the coil windings.

In the past, one of the methods for processing a wound, continuous stripcore has comprised first consolidating the core after winding into afirm, relatively rigid configuration by impregnating the core withepoxyresin or the like and then separating it into two parts .each of whichgenerally has a Cconfiguration, in the case where the consolidated coreis substantially rectangular in shape. The cut ends of thecomponentpa'rts of the severed core are then ground to a smooth finish,and one of the members, having a core leg about-which'it is desirablethat the coil be positioned,-is inserted'into a complementary centralopening of a previously wound coil. The separated members of the coreare then surrounded by a steel band which is first threaded through anopening-provided in the coil so that it completely surrounds the core.Clamping pressure is applied to the band with a suitable banding tool soas to properly align the core members and bring the severed ends intojuxtaposition.

In another well-known method for assembling a continuously wound coretype of inductor, the core, after winding, is cut in one position only,generally adjacent to one corner in the case of a rectangular core.Insertion of the coil is then effected by bending outwardly a leg of thecore adjacent to the cut so as to widen the gap therein sufficiently toallow proper insertion of the coil. After placing the coil over aselected leg, the core is bent back into its original arrangement andsecured in a relatively rigid position by banding and clamping. Such amethod imposes design limitations on the configuration of the coreinasmuch as one leg of the core must be relatively long in relation tothe core thickness in order that it may be opened up sufficiently toaccept the coil. Furthermore, this method has a disadvantage in that,

during the course of the operation of opening and closing of the core,there is a tendency to cold work the annealed laminations which maydecrease the permeability of the core and result in higher core losses.

Methods employed for constructing inducto'rsutilizing continuously woundcores and the configurations resulting therefrom, particularly thosemethods and configura tions discussed heretofore, are unsuited toeconomical production techniques in that the banding operation does notlend itself readily to automatic machine operations.

It is therefore an object of the invention to provide a method forassembling an inductor device having a core formed from continuouslywound magnetic strip material which is adaptable to automatic assemblytechniques.

It is a further object of the invention to providea method and means forsecuring precise alignment of a continuously wound magnetic core of aninductor device after the coil has been afiixed thereon, which meansarereadily adaptable to automatic assembly techniques.

It is yet another object of the invention to provide a combined clampingand mounting means for a magnetic core, said means providing a highdegree of control of the clamping pressure applied to the core members.

For a better understanding of the invention, together with other andfurther objects thereof, reference is made to the following detaileddescription taken in connection with the accompanying drawings, inwhich:

Fig. 1 is a side elevation ofan inductor embodying the principles of theinvention.

Fig. 2 is a top plan view of the inductor of Fig. 1.

Fig. 3 is an end elevation of the inductor of Fig. 1.

Fig. 4 is a sectional side elevation taken on the line "4-4 of Fig. 2.

Fig. 5 is a sectional-side elevation taken on the line 5 5 of Fig. 1.

Fig. 6 is a fragmentary perspective view of a portion of the inductorframe showing a step in the process of assembling the inductor of thepresent invention.

Referring now to the drawings, in-Fig. 1 a completely assembled inductoris shown in general outline. The inductor has a coil 10 which maycomprise a plurality of windings arranged in any suitable manner, suchas con centrically or in juxtaposition with one another, and may beimpregnated or covered with a suitable insulating material. The windingsmay be connected and arranged to provide a transformer, reactor, or anyother type of conductor as maybe desired. Connections may be made tocoil windings 1% by means of terminal leads 1.2. Windings it aredisposed about a continuously wound magnetic core 14 which is preferablyformed by winding a continuous strip of magnetic core material havingsuitable dimensions into a desired configuration which, for purposes ofillustration, is shown in the drawings as being substantiallyrectangular. As will be described in more detail hereinafter, the core14 is severed along the line 16 so that the windings it may be slippedover one leg thereof during the assembly process.

A channel frame 18 encases core 14 about three sides thereof. Frame 18may be stamped or bent from suitable sheet metal material of sufiicientrigidity so that it is adapted to hold an assembled core in lateralalignment. A securing member or strip 20 passes through the centralaxial opening in winding 16 and is positioned in alignment with oneperipheral surface of core 14 by means of ears or tabs 22. Frame 18 alsohas outwardly extending tabs 24, 26 which serve as brackets forconveniently and securely mounting the inductor unit where desired. Tabs24, 26 are integral with frame 18 and while these tabs are shown merelyfor purposes of illustration on only one end of the inductor, it isunderstood that other tabs may be provided wherever desired on frame 18.

the cut.

The method of assembly and the novel features of the inductor of thepresent invention formed by the steps of the method will now bedescribed in more detail.

To assemble an inductor embodying the teachings of the presentinvention, core 14 is first wound from a suitable magnetic stripmaterial into the desired configuration. Such material may be ironhaving special permeability or grain characteristics. With proper choiceof core material having a preferred grain orientation, winding a core ina continuous fashion allows twenty-five to thirty percent more flux thannon-oriented materials to be carried by the core for the samemagnetizing force. Such a continuously wound core is generallyrectangular in shape and is annealed after winding so that it willmaintain a stable configuration.

Since the rectangular core must be severed to allow placement of thecoil thereon, the core is first impregnated with a suitable bindingmaterial, such as an epoxy resin, which fills the interstices betweenthe windings and serves to consolidate them into a desired shape. Thecore is then cut at two places 16 lying in a common plane so as todivide it into two members having an I and a C shape 28, 30 respectively(Fig. 4). The surface areas exposed by cuts 16 are preferably ground toa high degree of smoothness in order to insure close contact with eachother when the core is again closed upon itself, so as to minimize airgap reluctance across However, it is understood that in someapplications an air gap of specified thickness may be desired.

. In such case, a suitable spacer may be inserted between the surfacesrepresented by cuts 16. Cuts 16 are preferably made as close aspractical to two of the inner corners or fillets of core 14 so as tofacilitate insertion of I-piece 28 in coil 10. By cutting core 14 in themanner described, automatic assembly by suitable machines is facilitatedsince the mounting of coil 10 on core 14 requires only one simple linearmotion of the I-piece 28 through the central axial opening of the coil10. Precise alignment in effecting this assembly operation is,therefore, not required since the curved outer contour of I-piece 28 atthe corners acts as a lead-in or guide which assists in insertion of theI-piece.

To assemble the coil 10 and core 14 in frame 18,

, the C-piece 38 may be inserted first in the channel ing of the frameinto a rectangular configuration without overlap. The open ends of frame13 have tabs 36 integrally formed thereon which, during the assemblysteps, are in an upwardly extending position, in order to allow core 14to pass freely into its nesting position within frame 18. After C-piece30 has been positioned in frame 18, I-piece 28 with associated coil 10is next inserted within the frame. Binding strip is then insertedthrough the central aperture of coil 18 and allowed to pass throughslots 38 in each side 40 of frame 18 ('Fig. 6). It will be noted thatsince the motion of binding strip 20 during the insertion operation isalso a simple linear one, the insertion operation is easily adaptable toautomatic machine assembly operations. The tabs 22 of strip 21) are thenbent downwardly and tightly against the sides 40 of frame 18, thusserving to apply a compressive force to frame 18 and bind it securely inposition about the core 1 4.

Upstanding tabs 22 on frame 18 are next pressed inwardly and tightlyagainst strip 28 with sufficient force to cause the strip directlybeneath tabs 36 to deflect into the spaces 42, formed by the corners ofthe core 14 and sides 40 of frame 18. This deflection of strip .28

serves to draw the sides 40 of frame =18 more tightly together but alsoallows freedom from close manufacturing tolerances for the componentelements of the inductor. This insures tightness of assembly even thoughthere may be some inaccuracy in the assembly operation. Accordingly, itwill be seen that precise alignment of all of the component parts whichform the inductor is not necessary to provide a tight and secure fit.

In the inductor shown in the drawings, frame 18 is provided with anupwardly extending tab or ear 24 having an aperture 44 therein formounting purposes, and a pair of outwardly extending wings 26 withapertures 46 therein. Bar 24 and wings 26 provide convenient mountingbrackets for mounting the inductor on electrical equipment wheredesired. It will be noted in the illustrated embodiment that car 24 hasan enclosed slot 38 therein for receiving an end tab 22 of strip 20whereas slot 38 in the opposite frame wall 40 (Fig. 6) has an open sideor mouth in order to facilitate linear insertion of closing strip 20through coil 11). However, a slot with an open side may be formed inboth walls 48 to receive strip 20 in applications where ear 24 is notneeded for mounting purposes.

It will be seen that the present invention provides a novel inductorassembly which is extremely compact and rigid, yet all motions employedin the assembly process are simple and linear in nature and thereforeare ideally suited for economical mass production assembly techniques,either by hand or by machine. It will be further noted that, althoughcore 14 shown for purposes of illustration was divided into C-Iportions, it is understood that a conventional double-C-member core maybe utilized in connection with the novel frame binding feature of theinvention or the conventional bent-leg type of continuous core may alsobe used with the binding frame of the present invention. It will also benoted that the C-I core separating arrangement of the present inventionfacilitates quick assembly of the component elements of an inductor andis readily adaptable to the wrapped band method of binding.

While the present invention has been disclosed by means of specificillustrative embodiments thereof, it would be obvious to those skilledin the art that various changes and modifications in the means ofoperation described or in the apparatus, may be made without departingfrom the spirit of the invention as defined in the appended claims.

I claim:

1. An electromagnetic induction device comprising a substantially closedloop magnetic core having rounded corners, a frame member partiallyencircling the outer periphery of said core with an open side exposingat least one of said rounded corners, said frame having slots thereinnear said open side, a closure member comprising a flat, resilient striphaving tab portions on each end thereof and extending across the openingof said frame to complete the enclosure of said core, the ends of saidclosure strip passing laterally through said slots in said frame, saidframe having means for preventing outward movement of said closuremember away from said core when in assembled relationship, said tabportions being bent into locked contact with the walls of said frame,said closure member having an indented deformation projecting inwardlytowards said rounded corner of said core to cause pressure to be exertedagainst said core and tension applied to said tabs to maintain constantpressure against the sides of said frame.

2. An electromagnetic induction device comprising a substantially closedloop magnetic core having rounded corners, a frame member partiallyencircling the outer peniphery of said core with an open side exposingat least one of said rounded corners, said frame having slots thereinnear said open side, a closure member comprising a fiat, resilient striphaving tab portions on each end thereof and extending across the openingof said frame to complete the enclosure of said core, the ends of saidclosure strip passing laterally through said slots in said frame, saidframe having means for preventing outward movement of said closuremember away from said core when in assembled relationship includingoutwardly extending tabs disposed adjacent said rounded corners andadapted to be bent over said closure member and in contact therewith,said strip tab members being bent into locked contact with the walls ofsaid frame, said closure member being inwardly deformed towards saidrounded corner of said core by the bending of said frame tabs thereover,to exert pressure against said core and apply tension to said tabs tomaintain constant pressure against the sides of said frame.

References Cited in the file of this patent UNITED STATES PATENTS ForbesMar. 20, 1945 White et al. Jan. 22, 1946 Ford Nov. 15, 1949 Epstein Aug.7, 1951 Epstein Oct. 23, 1951 Ford Feb. 19, 1952. Dunn Oct. 20, 1953

